Method for the determination of the pressure in and/or of the through-flow through a pump

Abstract

In the method for the determination of the pressure (p) in and/or of the through-flow (Q) of a liquid through a pump having at least one magnetic bearing for the axial journaling of the pump rotor ( 1 ), axial forces act on the rotor ( 1 ) of the pump during operation. The axial forces which act on the rotor are utilised for the determination of the pressure (p) and/or of the through-flow (Q).

What is claimed is:  
     
       1. A method for the determination of one of through-flow (Q) of a liquid through a pump and through-flow (Q) as well as pressure (p) of a liquid in a pump the pump having a pump rotor, a drive rotor ( 1 ) and a drive stator ( 2 ), comprising the steps of: 
       axially journaling the pump rotor and drive rotor ( 1 ) with at least one passive magnetic bearing;  
       determining the magnetic drive flux (Φ M ) in the gap between the drive rotor ( 1 ) and the stator ( 2 );  
       determining the drive current (I A );  
       determining the drive torque (M) from the drive flux (Φ M ) and the drive current (I A ); and, determining the through-flow (Q) from the drive torque (M) and the speed of rotation (ω) of the rotor.  
     
     
       2. A method for the determination of one of pressure (p) of a liquid in a pump and pressure (p) as well as through-flow (Q) of a liquid through a pump, the pump having a pump rotor ( 1 ), comprising the steps of: 
       axially journaling the pump rotor with at least one magnetic bearing; and,  
       utilizing axial forces acting on the rotor ( 1 ) due to a pressure difference between the pump inlet side and the pump outlet side and speed of rotation (ω) to determine pressure (p).  
     
     
       3. A method for the determination of one of through-flow (Q) of a liquid through a pump and though-flow (Q) as well as pressure (p) of a liquid in a pump, the pump having a pump rotor ( 1 ), comprising the steps of: 
       axially journaling the pump rotor ( 1 ) with at least one passive magnetic bearing;  
       determining the axial deflection (z, Δz) of the rotor ( 1 );  
       determining the drive current (I A );  
       determining the drive torque (M) from the drive current (I A ) and the axial deflection (z, Δz) of the rotor ( 1 ); and,  
       determining the through-flow (Q) from the drive torque (M) and the speed of rotation (ω) of the rotor.  
     
     
       4. The method according to  claim 2  including the further step of: 
       using the pressure (p) and the respective speed of rotation (ω) for determining the flow-through (Q) of the pump via the pressure-through-flow characteristics of the pump.  
     
     
       5. The method according to claims  4  or  3  and including the further step of: 
       determining the viscosity (η) of the liquid in the pump for the determination of the through-flow (Q) from one of the previously established pressure (p) together with the associated speed of rotation (ω) and the torque (M) together with the associated speed of rotation (ω).  
     
     
       6. The method according to  claim 5  and including the further steps of: 
       determining a first liquid pressure (p) by the axial forces which act on the rotor ( 1 );  
       determining a second liquid pressure (p) from the established torque (M) and the established speed of rotation (ω); and,  
       determining viscosity (η) from the difference of the first liquid pressure and the second liquid pressure and from the associated speed of rotation (ω).  
     
     
       7. The method according to  claim 5  including the further steps of: 
       determining liquid damping (D FL ) which acts on the rotor ( 1 ); and,  
       determining viscosity (η) from the liquid damping (D FL ).  
     
     
       8. The method in accordance with  claim 7  and including the further step of: 
       determining the liquid damping (D FL ) with shifting eigen frequencies of the rotor.  
     
     
       9. The method in accordance with  claim 7  and including the further steps of: 
       operating the rotor at an eigen frequency;  
       measuring the deflection (z, Δz) at the eigen frequency; and,  
       determining the liquid damping (D FL ) from the deflection (z, Δz).  
     
     
       10. The method in accordance with  claim 7  and including the further steps of: 
       varying the speed of rotation (ω) of the rotor ( 1 ) with different frequencies;  
       determining the variation of the axial bearing forces or of the axial deflection respectively which arises at the respective frequency of variation of the speed of rotation (ω); and,  
       determining the liquid damping (D FL ) from the variation of the axial bearing forces or of the axial deflection respectively at the different frequencies of variation of the speed of rotation (ω).  
     
     
       11. The method in accordance with  claim 7  and including the further steps of: 
       determining the displacement of the stability boundary of the control circuit for the axial magnetic journaling of the rotor ( 1 ); and,  
       determining a liquid damping (D FL ) from the displacement.  
     
     
       12. The method in accordance with  claim 5  and including the further step of: 
       utilizing determined viscosity (η) for the determination of through-flow (Q).  
     
     
       13. The method according to  claim 4  including the further steps of: 
       storing the pressure-through-flow characteristics of the pump in an electronic look-up table; and,  
       looking up the flow-through (Q) of the pump which results from the determined pressure (p) and the respective speed of rotation.  
     
     
       14. The method according to  claim 4  including the further steps of: 
       representing stored pressure-through-flow characteristics of the pump in a polynomial; and,  
       determining the flow-through (Q) by evaluating the polynomial for the determined pressure (p) and the respective speed of rotation.  
     
     
       15. The method according to  claim 2  including the further steps of: 
       passively journalling the pump rotor ( 1 ) with the magnetic bearing for the axial journaling of the pump rotor ( 1 ); and,  
       measuring the axial deflection (z, Δz) of the rotor ( 1 ) to measure the axial forces on the rotor ( 1 ).  
     
     
       16. The method according to  claim 3  and including the further steps of: 
       providing sensors (S 1 , S 2 , S 3 , S 4 ) for the determination of the direction of the magnetic field in the gap between a rotor ( 1 ) and a stator ( 2 ); and  
       using sensors (S 1 , S 2 , S 3 , S 4 ) for the determination of the axial deflection (z, Δz) of the rotor ( 1 ).  
     
     
       17. The method according to claims  15  or  16  wherein the sensors (S 1 , S 2 , S 3 , S 4 ) provided are Hall sensors. 
     
     
       18. The method according to  claim 15  and including the further steps of: 
       storing the measured axial deflections (z, Δz) of the rotor ( 1 ) at different speeds of rotation (ω) as well as pressures (p) resulting therefrom in an electronic look-up table;  
       measuring the axial deflection (z, Δz) of the rotor ( 1 ) and speed of rotation (ω) during operation; and,  
       looking up the pressure (p) which results from the axial deflection (z, Δz) and speed of rotation (ω).  
     
     
       19. The method according to  claim 15  and including the further steps of: 
       representing the measured axial deflections (z, Δz) of the rotor ( 1 ) at the different speeds of rotation (ω) as well as the pressures resulting therefrom in a polynomial;  
       measuring the axial deflection (z, Δz) of the rotor ( 1 ) and speed of rotation (ω) during operation; and,  
       determining the pressure (p) which results from the measured axial deflection (z, Δz) and speed of rotation (ω) by evaluating the polynomial.  
     
     
       20. The method according to  claim 15  and including the further steps of: 
       providing sensors (S 1 , S 2 , S 3 , S 4 ) for the determination of the direction of the magnetic field in the gap between a rotor ( 1 ) and a stator ( 2 ); and,  
       using sensors (S 1 , S 2 , S 3 , S 4 ) for the determination of the axial deflection (z, Δz) of the rotor.  
     
     
       21. The method according to  claim 2  including the further steps of: 
       actively journaling the pump rotor ( 1 ) with the magnetic bearing for the axial journaling of the pump rotor ( 1 ); and,  
       measuring the axial forces on the rotor ( 1 ) by measuring the bearing current required for the axial journaling of the rotor.  
     
     
       22. The method according to  claim 21  and including the further steps of: 
       storing the measured bearing currents at different speeds of rotation (ω) as well as pressures resulting therefrom in an electronic look-up table;  
       measuring the bearing current and speed of rotation (ω) during operation; and,  
       looking up the pressure (p) which results from the bearing current and speed of rotation.  
     
     
       23. The method according to  claim 21  and including the further steps of: 
       representing the measured bearing currents at different speeds of rotation (ω) as well as pressures resulting therefrom in a polynomial;  
       measuring the bearing current and speed of rotation (ω) during operation; and,  
       determining the pressure (p) which results from the measured bearing current and speed of rotation by evaluating the polynomial.  
     
     
       24. The method according to  claim 3  including the further step of: 
       determining pressure (p) from the already established through-flow (Q) and the associated speed of rotation (ω) via the pressure-through-flow characteristics of the pump.  
     
     
       25. method according to  claim 24  including the further steps of: 
       storing the pressure-through-flow characteristics of the pump in an electronic look-up table; and,  
       determining the pressure (p) from the already established through-flow (Q) and the associated speed of rotation (ω) with the help of the electronic look-up table containing the pressure-through-flow characteristics.  
     
     
       26. The method according to  claim 25  including the further steps of: 
       approximating the pressure-through-flow characteristics with a polynomial; and, determining the pressure (p) by evaluating the polynomial for the established through-flow (Q) and the associated speed of rotation (ω).  
     
     
       27. The method according to  claim 3  and including the further steps of: 
       storing different drive currents (I A ) at different axial deflections (z, Δz) of the rotor and the respective torque (M) resulting therefrom in an electronic look-up table;  
       measuring the axial deflection (z, Δz) of the rotor ( 1 ) and the respective drive current (I A ) during operation of the pump;  
       determining the torque (M) from the drive current (I A ) and the axial deflection (z, Δz) of the rotor ( 1 ) with the help of the look-up table; and, determining the through-flow (Q) through the pump from the torque (M) and the speed of the rotation (ω) of the rotor.